The present invention relates to a telecommunication system including at least one transmitter and one receiver respectively intended to transmit and receive a signal formed by at least one pulse sequence modulated by symbol encoding means included in the transmitter.
Such telecommunication systems are currently studied with the aim of assessing the relevance of so-called Ultra-Wide Band transmission techniques (further referred to as UWB systems and techniques, respectively). In such a system, each transmitter may be identified by a signature formed by chip numbers identifying respective positions of the pulses within associated time windows, which signature is in itself quite sturdy and may thus be reliably and accurately communicated to all potential receivers.
The pulses used in UWB systems are very short, having for example a duration lower than 1 nanosecond, which offers to such systems bandwidths at least as large as 7.5 GigaHertz, entailing high flexibility and hence numerous possible applications for such systems.
A pulse sequence as described above may form a carrying signal on which information can be encoded by modulation of said carrying signal. The inventors have observed that, because of the shortness of the pulses involved, a precise synchronization with a given pulse sequence may be difficult to perform at the receiver end, so that the chosen modulation scheme should preferably involve as few time-related parameters as possible in order to be cost-efficient. The inventors thus have chosen a modulation scheme according to which the information carried by pulse sequences may be recovered at the receiver end without having to map precisely, with respect to time, the received pulse sequences, which purpose is achieved by multiplying each pulse sequence by a value representative of a symbol to be carried by said pulse sequence, so that the information carried by signals transmitted accordingly may essentially be represented by the power carried by these signals, which power is related to the amplitude of the pulses included within such a signal.
Another problem to be solved is linked to the large bandwidth of the carrying signal to be used according to the principles described above. Indeed, it is very difficult, if not utterly impossible in the known state of the art, to design electronic circuits and antennas having invariant physical properties over a 7.5 GigaHertz bandwidth, e.g. a constant gain which is necessary for ensuring a same quality of service for all users of the system regardless of the carrying frequency chosen for each user.